ROSS: TROPHIC ONTOGENY OF LEOPARD SEAROBIN 



predators of large prey. The data suggest a switch 

 in feeding strategy to an energy maximizer (cf. 

 Griffiths 1975) in which predators feed in such a 

 manner as to maximize their energy intake. In P. 

 scitulus this is perhaps accomplished by a switch 

 in feeding behavior after achieving a critical size 

 threshold requisite for capturing partially buried 

 infaunal prey. 



The shift to utilization of large prey occurs 

 slightly before the onset of reproduction. In- 

 creased energy demands, or a decrease in foraging 

 time, brought about by gonadal development and 

 breeding activity or both, might be critical factors 

 in selecting for the change in the feeding strategy 

 of P. scitulus. 



Mature and immature P. scitulus were effec- 

 tively segregated along both spatial and trophic 

 dimensions in Tampa Bay. Spatial segregation 

 might occur through the ability of juvenile searob- 

 ins to occupy shallower water or to withstand 

 lower salinity, a characteristic of many juvenile 

 marine fishes (Gunter 1961). Trophic overlap in 

 prey kind between immature and mature size 

 groups was closely comparable with trophic over- 

 lap between adult individuals of different species 

 of searobins on the West Florida Shelf (Ross 1977). 

 Consequently, P. scitulus in Tampa Bay were ef- 

 fectively reducing the potential for intraspecific 

 competition. 



ACKNOWLEDGMENTS 



This study is based, in part, on a segment of my 

 doctoral dissertation submitted to the University 

 of South Florida. I thank my major professor, J. C. 

 Briggs, and committee members, D. G. Burch, B. 

 C. Cowell, R. W. McDiarmid, and A. J. Meyer- 

 riecks for their help. 



I thank B. C. Cowell and S. A. Bortone for help- 

 ful comments on an early draft of this paper. The 

 University of Southern Mississippi Ecology 

 Forum contributed many helpful comments to a 

 later draft. I am especially grateful to my wife 

 Yvonne for her help during all phases of this 

 study. The program for cluster analysis was writ- 

 ten by J. G. Field, who is gratefully acknowledged. 



LITERATURE CITED 



Bray, J. R., and J. T. Curtis. 



1957. An ordination of the upland forest communities of 

 southern Wisconsin. Ecol. Monogr. 27:325-349. 



Carr, W. E. S., and C. a. Adams. 



1973. Food habits of juvenile marine fishes occupying 



seagrass beds in the estuarine zone near Crystal River, 

 Florida. Trans. Am. Fish. Soc. 102:511-540. 



Darnell, R. M. 



1958. Food habits of fishes and larger invertebrates of 

 Lake Pontchartrain, Louisiana, an estuarine communi- 

 ty. Publ. Inst. Mar. Sci. Univ. Tex. 5:353-416. 



Griffiths, D. 



1975. Prey availability and the food of predators. Ecol- 

 ogy 56:1209-1214. 



Gunter, G. 



1961. Salinity and size in marine fishes. Copeia 

 1961:234-235. 

 Hartman, G. F. 



1958. Mouth size and food size in young rainbow trout, 

 Salmo gairdneri. Copeia 1958:233-234. 

 HELLAWELL, J. M., AND R. ABEL. 



1971. A rapid volumetric method for the analysis of the 

 food of fishes. J. Fish Biol. 3:29-37. 



Hespenheide, H. a. 



1973. Ecological inferences from morphological data. 

 Annu. Rev. Ecol. Syst. 4:213-229. 

 HUBBS, C. L., AND K. F. LAGLER. 



1958. Fishes of the Great Lakes region. Revised ed. 

 Cranbrook Inst. Sci. Bull. 26, 213 p. 



HURTUBIA, J. 



1973. Trophic diversity measurement in sympatric pred- 

 atory species. Ecology 54:885-890. 



IVLEV, V. S. 



1961. Experimental ecology of the feeding of fishes. 

 (Translated from Russ.) Yale Univ. Press, New Haven, 

 Conn., 302 p. 



keast, a., and d. Webb. 



1967. Mouth and body form relative to feeding ecology in 



the fish fauna of a small lake, Lake Opinicon, Ontario. J. 



Fish. Res. Board Can. 23:1845-1874. 

 NORTHCOTE, T. G. 



1954. Observations on the comparative ecology of two 



species of fish, Cottus asper and Cottus rhotheus, in British 



Columbia. Copeia 1954:25-28. 

 PALOHEIMO, J. E., AND L. M. DICKIE. 



1966. Food and growth of fishes. III. Relations among food, 



body size, and growth efficiency. J. Fish. Res. Board Can. 



23:1209-1248. 



Parker, R. R., and P. A. Larkin. 



1959. A concept of growth in fishes. J. Fish. Res. Board 

 Can. 16:721-745. 



PlELOU, E. C. 



1966. The measurement of diversity in different types of 

 biological collections. J. Theor. Biol. 13:131-144. 

 REID, G. K., Jr. 



1954. An ecological study of the Gulf of Mexico fishes, in 

 the vicinity of Cedar Key, Florida. Bull. Mar. Sci. Gulf 

 Caribb. 4:1-94. 

 RICKER, W. E. 



1975. Computation and interpretation of biological statis- 

 tics offish papulations. Fish. Res. Board Can., Bull. 191, 

 382 p. 

 Ross, S. T. 



1974. Resource partitioning in searobins (Pisces: Trig- 

 lidae) on the west Florida shelf Ph.D. Thesis, Univ. 

 South Florida, Tampa, 205 p. 



1977. Patterns of resource partitioning in searobins 

 (Pisces: Triglidae). Copeia 1977:561-571. 



In press. Searobins (Pisces: Triglidae). Mem. Hourglass 

 Cruises. 



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